Illusionary wall

The illusionary wall spell creates the illusion of a wall, floor, ceiling, or similar surface, which is permanent until dispelled. It appears absolutely real when viewed (even magically), but physical objects can pass through it without difficulty. When the spell is used to hide pits, traps, or normal doors, normal demihuman and magical detection abilities work normally, and touch or probing searches reveal the true nature of the surface, though they do not cause the illusion to disappear.

Note: This version of illusionary wall originally appeared in the 2nd Edition Player's Handbook for Advanced Dungeons & Dragons from TSR. Its use here is for the purposes of providing context for the campaign only.